Oil-heating furnace



Feb. 23,1926. 1,574,546

J. E. BELL OIL HEATING FURNACE l Filed Jan. 28, 1922 3 ShetS-Sheet 1 IIIIIHIIIII Feb. 23 1926.

J. E. BELL O IL HEATING FURNAGE 3 Sheets-Sheet 2 Filed Jan. 28, 1922 Feb; 23 i926.

J. E; BELL OIL HEATING FURNACE 3 Sheets-Sheet 5 'Filed Jan. 28

' sponding increase in the distillate produced. y

proximately 100 pounds lper square inch and- `any break or rupture is followed by disas- Patented Feb. 23, 1926.

VUNITED STATESv PATENT OFFICE.

JOHN E. BELL, OF BROOKLYN,v NEW YORK, ASSIGNOR T0 SINCLAIR REFINING COM- PANY, OF CHICAGO, ILLINOIS. A CORPORATION OF MAINE.

OIL-HEATING FURNACE.

To all whom 'it may concern.'

Be it known that I, JOHN E. BELL, a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New. York, have invented certain new and useful Improvements in Oil-Heating Furnaces/of which the following is a specification.

My invention relates more particularly to pressure stills used for the purpose of cracking hydrocarbons of higher boiling points such as crude petroleum, gas oil and the like, to form more Volatile or lighter hydrocarbons suoli as those thatconstitute commercial gasoline and has specifically for its object to protect the tubes from overheating or burning and to lengthen the time of the runs between cleaning with a corre- Stills for cracking oil are heated by furnaces in which coal, gas or oil4 is burned and for economy in fuel consumption it is desirable that the fuel be burned in the furnace with the least amount of excess, air and the maximum. furnace temperature.` When there is a fresh charge of oil in the stills free from carbon this can be done Without fear of injury to the tubes or other heat absorbing portions of the still. When, however, carbon is' formed in the process and is deposited on the inside of the tubes or heating elements of the still as in the case of cracking stills, this condition no longer' exists as the coating of carbon or heavy tar is a poor conductor of heat and insulates the metal surface from the oil on the inside with the results that the temperature of the metal increases over the temperature of the oil, the amount of this-increase .being proportional to the thickness of the carbon deposit and to the amount of heat delivered to the external surface heated from the furnace. It follows that unless stills are frequently shut down for cleaning or the temperature of the furnace itself is reduced it is ldiilicult to maintain the stills in operation for a sufficient length of time to make such opration commercially practical. There is also a hazard to life and property due to the possible bursting of a tube which has become overheated and burnt, as the pressure in the stills is maintained at aptrous lire. The tubes or other heating surfaces .most exposed to the heat of the .fur-v nace will be the first to suffer and it is thc object of my invention to reduce the amount of heat absorbed by these tubes or surfaces and increase the amount of heat absorbed by theother portion of the still without sacriiicirlig either fuel. economy or capacity of the stil It is Well known that with thel ordinary arrangement of furnace such as used for heating boilers and heretofore used under stills a large proportion of the heat in the fuel passes directl from the fuel-bed, Where solid fuel is use or from the flame and hotter brick work when gaseous or oil fuel is used, direct to the heat4 absorbing surface of the boiler or still by radiation and it has been shown by tests that the amount of heat absorbed by the tubes next to the fire in a boiler may be and usually is forty or fifty times as great as the average absorption of heat throughout the Whole surface, and this amount of heat is principally transferred as radiant energy. It has also been shown that heat transferred in this Way increases very rapidly With the furnace temperature; the process in general being controlled by Stefans law -for radiation which makes the 'there is an actual increase in gas temperature entering the cooling surface of the broiler or still, butthis increase in gas temperature does not compensate for the reduction in the radiant heat so that as a net result the surface of first contact would not absorb as much heat.

In my improved form of still the heat absorbing surface is protected from the direct radiation of the furnace by the interposition of a high bridge Wall and a vertical fiuewith refractory Walls, in its preferred arrangement, although other forms of passages and screens might be used. To still further protect the still surfaceiof first contact with the furnace gases, I Lintroduce a diluting body of air or gas into the connecting fiue, at a point near the furnace. This reduces the gas temperature and also the temperature of the refractory walls. The heat absorbed by the 'surface first in contact with the furnace gases is thus reduced in two ways; namely, by the lower temperature of the gas and second, by a reduction in the temperature of the refractory secondaryradiating surfaces. If the diluting gas is not heated, the obvious result is a reduction in efficiency such as accompanies the burning of fuel with an excessive amount of air. I have found, however, by experiment that if the ten'iperature of the diluting gas is approximately the temperature of the waste gases leaving the still surface that not only is there no reduction in the fuel economy and capacity but onv the other hand there is a slight increase in both.

I mayuse either one of two methods for supplying the dilutant gas at the proper temperature. In one way of applying this invention a proportion of the waste gas at the temperature at which it leaves the still is drawn aside and returned to the furnace. The other way is toinstall an air-heater in the flue leading from the still and to force through this heater the air that is used as a diluting medium thus heating it to the proper temperature before forcing it into the flue between the furnace and still. Referring to the first method it is obvious that when the same amount of fuel is burned in the furnace that a measure of efficiency and capacity of the still can be made from the temperature and weight of the waste gases. The weight of the gases is not, however, changed in my improved heater and experience and theory .show that this temperature is reduced. In a still in which oil is mechanically circulated the temperature of the heat absorbing surface differs little from that of the oil which for the purpose of calculation can be considered as uniform. The heat transfer equations show that the difference in temperature between the waste gases and the oil is proportional to the difference in temperature between the furnace gases entering the heater and the oil, and to a factor in which the ratio between the heat transfer rate and the gas weight appears., Tests have shown that the heat transfer rate and the gas weight is in turn proportional to the gas flow or with afixed surface, to the gas weight and as a .consequence this ratio and the second factor are practically unchanged ,when this device is used. It, therefore, follows that for the same heat absorption the exit temperature of the gases will be reduced as the inlet temperature is reduced and this, as has been pointed out above, has proven true in practice.

IVhen air is used for the dilutant fluid it is practical to bring this air, by the use of a waste gas heater, to approximately the temperature of the gases leaving the still. lVhen this is done the argument just made applies and the efficiency and capacity of the still is slightl i increased. Vhen the air-heater is smal er and the temperature of the air is not raised to this point there may be a slight reduction in the efficiency and capacity. In view of this fact and in view further of the fact that with the first method the air-heater is eliminated I prefer returning a portion of the waste gases to the furnace, but it is entirely possible that conditions would arise which would make it desirable to use' the air-heater method so that, in the more comprehensive claims, I claim both methods in combination with the flue passage asl within my invention.

Increasing the gas flow over the heating surface by the use of either arrangement increases the friction loss and to maintain the same furnace draft it is necessary to have an increased draft at the still outlet. 'hen this is provided for not only will the capacity of the still be maintained when this device is in use, but the efficiency will be slightly increased and on account of the lower temperature of the gases striking the first tubes of the heater the tubes will be protected.

The invention in its broader aspects is independent of the particular form of still system with which the heating device iS used. As an instance of an oil still in which it may b employed to particular advantage reference may be made to Patent No. 1,285,- 200 granted to the Sinclair Refining Company, November 19, 1918, on the application of Edward W. Isom. In the accompanying drawings I have shown a preferred form of my invention in which the gases coming from the fire-box are tempered by an admixture of products of combustion which have been more or less cooled by circulation through the heating chamber in contact with the oil tubes therein, and also an example of a somewhat similar furnace in which the gases are tempered by an admixture of airl preheated by means of the waste gases from the furnace. It is to be understood, however, that these specific disclosures are for the purpose of exemplitication only and that the scope of the invention is defined in the following claims, in which I have endeavored to distinguish it from the prior artV so far as known to me, without, however, relinqulshing or abandoning any portion or feature thereof.

Figure 1 shows in longitudinal, vertical section a furnace embodying that form of my invention in which the gases from the fire-box are tempered by the return of a portion ofthe spent gases; Fig. 2 is a similar view of a somewhat different type of oil heating furnace in which the gases from the fire-box are tempered by means of pre-heated air, Fig. 3 is a transverse, vertical section of the same on the line 3 3 of Fig. 2; Fig. 4 a horizontal section on the line 4-4 of Fig. 2, and Fig. 5 a fragmentary sectional view on the vertical plane of line 5-5 of Fig. 4.

Referring to the form of the invention shown .in Fig. 1 of the drawing, the furnace comprises a fire-box 1 which may be of any usual or preferred form, communicating by an elongated throat 2 with the heating fiue or chamber 3 containing the oil heating tubes. The chamber 3 is of considerable vertical length and communicates at its lower eii-d with a Stack flue 4. I have shown the fire-box as equipped at 5 with a mechanical stoker and at 5L with burners, by means'of which oil or gas may be used as a fuel. The elongated throat 2 is separated from the heating iiue vor chamber 3 .by a lengthy bridge-Wall 6 which overliangs at its top as at'30 into the throat of the fire-box. The purpose of the elongated throat and overhaiiging bridge-wall is to shield the tubes in the heatingflue from direct radiation from the fire-box.

The battery of heating tubes 7 is connected at top and bottom to headers 9, 12, respectively, both of which headers are outside the heating flue. The tubes 7 extend through an opening 8 in the top wall'of the furnace, which-is closed by a perforated slab 8a of refractory material through which the tubes extend. At their lower ends the .tubes 7 extend through a slab of refractory material 10 beneath which the header 12 is located. The slabs of refractory material rest upon eollars forme-d on the tubes as shown in the view, and the lower plate or slablO rests upon angle irons 13 at its edges. The entire battery of tubes is sustained from the top header so as to be free to expand and contract with change of temperature. The top header is supported upon I-beam 9a on top of the furnace. The lower header is connected to a manifold 12a which receives oil through' the pipe 12". The upper header is connected to a manifold 9", which in turn connects with a pipe or pipes 11. The oil received through pipe 121 enters the header, flows upward through the bank of tubes to the upper header and thence through the manifold and pipe 11. lVhen the heater is employed in a systemof the type shown in the Isom patent to which reference has been made, the pipes 11,

12" are connected to the bulk supply tank,v such as shown at C in the patent and preferably one or both of them are provided with means for accelerating the circulation. as shown 1n said patent. The heating flue is provided with bafiies 14. 15 which cause the hot gases to pass backandr forth among the tubes of the battery a number of times,

reaching the stack flue 4, by which they make their exit. i

By reason of this thorough circulation among, and contact with the oil heatingr tubes, the heat is eiiiciently extracted from the products of combustion before they reach the stack flue, and the eiciency of the device is further increased due to the fact that the general direction of flow of the heating gases and oil is opposed so that the relatively cool oil entering at the bottom of the tubes extracts the heat from the partially cooled gases and its temperature increases until it is at the maximum in the upper pass of the furnace where it is exposed to the gases fresh from thefire-box. As heretofore observed, however, the oil heating tubes are screened from direct radiationfrom the firebox, even at their upper ends, thus preventing overheating with the consequences to which reference has heretofore been made.

IIn order to further reduce the temperature of the hot products of combustion, coming from the fire-box before they strike the oil containing tubes, I provide, in the form ofA my invention shown in Fig. 1, means for returning a portion of the partially cooled gases from the exit end of the heating chamber -and mixing it with the fresh products of combustion from the firebox. For thispurpose I provide a return Hue or flues 16 on one or both sides of the furnace, which connect with the lower end of the heating chamber at 17 and with a transverse iue vor boxing 18 extending across the throat of the fire-box. This boxing is formed with a longitudinal opening or openings 19, communicating with the throat' of the furnace. A forcing means of any desired or well-known character is interposed in each of the fiues 16. In the exemplification of the invention shown in Fig. 1 I have shown a common venturi construction at 20, for this purpose. By suitably controlling the forcing means any desired proportion of the products of combustion may be returned to and interminloo llt).

gled with the hot gases rising from. the Y fire-box. By this means, as above pointed out, I am enabled to temper the hot gases to any point desired, pre-venting overheating of the tubes at the upper pass and particularly the front tubes thereof, without reducing the thermal eficiency of the furnace, as pointed out in the opening paragraphs of the specification. By thus returning a portion of the products of combustion the volume of gases in contact with the tubes and consequently the rapidity of flow is in-.. creased and, therefore, the heating effect is improved and at the same time the heat is more evenly distributed throughout the` tubes and throughout the length thereof.

In the embodiment of the invention illusstated, instead ot' mixing cool products of con'ibustion with the hot gases from the tirebox arrangements are made for preheating a volume of air by the waste gases andmixing the air so preheated with the gases from the lire-box. I have shown this form of the invention as applied to a somewhat different form of heating furnace in which the oil ,tubes instead of being vertical are. horizontal butI it ywill be obvious that this means of temperii'ig the hot products of combustion could be employed in a. furnace which is otherwise like that shown in Fig. 1.

ln this second embodiment of the invention illustrated in Figs. 2 to 5 inclusive, thc general arrangement ot thc furnace including the lirebox l. elongated vertical throat 2 and downwardly extending heating flue 3 with baffles 14 and 15 is substantially like the furnace heretofore described. The oil heating tubes 7, however, are arranged horizontally in the heating flue and connect series of headers 3G, 36, etc., 37, 37, etc., arranged respectively in openings 38 and 39 formed in opposite side walls of the heating line. The openings are closed outside the headers by doors 4l of suitable material. The lowermost header on the lefthand side of the furnace, as seen lin Fig. 3 is provided with a connection 42 to serve as an inlet for the oil, and the upper header is provided with a similar connection 43 to serve as an outlet for the oil. It will be noted that the uppermost and lowermost headers on the left-hand side of the furnace, in other words those to which the inlet and outlet are respectively connected, receive only two horizontal rows of pipes whereas the intermediate headers on the same side and all of the headers on the other side of the fhurnace receive four horizontal rows of pipes. This provides for a continuous circulation of the oil received through the inlet 4Q back and forth across the'heating chamber in its passage to the outlet 43 so that 1t 1s exposed many times in its passage .Y through the furnace to the heat of the prodncts of combustion circulating about said pipe in its zig-zag passage from the top to the bottom of the heating flue.

In the form of the invention now under consideration the stack -flue 4L communicates with a vertical flue 4() which, at its upper end connects with a horizontal iue 3l leading to the stack. A battery of vertical tubes 32 is arranged in thisqvertical flue and communicates at its upper end with a boxing or flue 33 through which the pipes are supplied with air. The lower end of the tubes communicate through a header 35 with a horizontal flue 34 leading to an outlet 34a in front of the bridge Wall. The spent gases from the bottom of the heating chamber pass up the vertical flue 40 and heat the fine 32 therein. The air yentering the flue 33 flows counter-current to the gases down the pipes 32 and into the flue 34 along which it flows to the outlet 34n where it intermingles with and tempers the hot products of combustion from the firebox. Obviously, in this form of oil heating furnace, instead of preheating air in this manner and discharging it into the irebox a portion of the Cooled products of combustion from the lower end of the heating chamber might be returned to the firebox, as in the previously-described form of the invention.

In both forms of the invention as hereto- ,fore pointed out, I provide for returning thc hot gases to the lircbox and shieldingr thc tubes from direct radiation, and furthermore I cause the oil to flow countercurrent to the products of combustion whereby, as pointed out in the opening paragraph of the specification, the heat absorption is distributed as evenly as possible throughout the oil heating element and overheating of any portion thereof is prevented.

I claim:

1. A tubular oil cracking still having a heating chamber, a series ot oil heating tubes adapted to be externally heated extending therethrough, a tire box communicating with one end of said heating chamber, a flue communicating with the other end of said heating chamber, and means connecting said heating chamber near the flue end thereof with the tire box for returning a portion of the heating gases from the heating chamber to the fire box, whereby the heating gases from the fire box are temp-ered by the returned hot gases of lower temperature and the .resulting mixture is passed through the heating chamber.

2. An oil cracking still having a heating chamber, oil heating surfaces adapted to be externally heated therein, an inlet and an out-let to the heating chaniner, a lire box communicating with the heating chamber at. the inlet, a flue communieating with the outlet of the heating chamber, a flue connecting the heating chamber near the outlet with the fire box, and means for causing a return of a portion of the products of combusl tion from the heating chamber through said flue to the fire box, whereby the heating gases from the tire are tempered by the returned hot gases of lower temperature and the resulting mixture is passed through the heating chamber.

3. A tubular oil cracking still having a heating chamber, an inlet and an outlet to the heating-chamber, a fire box communieating with said chamber at the inlet thereoffa. flue communicating with said chamber near the outlet thereof, a series of oil heating tubes adapted to be externally heated extending through said heating chamber, a flue connecting the said heating chamber near its outlet with the lire box, and means mixture for forcing the return of la portion of the products of combustion' from the heating chamber through said flue to the fire box, whereby the heating gases from the lire box are tempered by the returned hot gases of lower temperature and the resulting is passed through the heating chamber. 4

4. A tubular oil cracking still having a heating chamber, a seriesv of oil heating tubes adapted to be externally heated extending through. said chamber, a lire box adjacent said chamber and communicating therewith at itsupper end, an, elongated bridge wall preventing direct radiation from the fire box againstsaid tubes, a flue connected to the lower end of said heating chamber, and means for returning part of the heated gases from near the lower end ot the heating chamber and introducing them t0 mix with the heating gases from the lire box, whereby lthe heating gases are ntempered by the returned hot gases of lower temperature and the `resulting mixture is passed through the heating chamber. l

5. A tubular oil cracking still having a heating chamber, a series ot vertical oil heating tubes adapted to be externally heated extending through said heating chamber, a flue communicating with the lower end of said heating chamber, a lire box having an elongated vertical throat communi' catino at its upper end with said heating chamber, a flue connecting the lower end of the heating chamber with lthe lower end of `the throat, and means in said flue for forcing the return ot partially cooled but'still hot gases to the fire box, whereby the heating gases from the. fire box are tempered by the returned hot gases of lower temperature and y the resulting mixture is passed through the heating chamber.

6. A tubular oil cracking still having a heating chamber, a series of oil heating tubes adapted to beexternally heated extending vertically therethrough, means on top of said chamber for supporting the heating tubes, a flue communicating with the lower end of the heating chamber, a lire box communicating with the upper end ot the heating chamber, baffle plates in the heating chamber for causing thc products ot combustion to pass backward and forward over V said heating tubes, and means for returning a portion ot' the products of combustion from near the bottom of the heating chamber to lthe lire box whereby the heating gases from the lire box are tempered by the return-ed hot gases of lower temperature and the resulting mixture is passed through the heating chamber.

7. A tubular oil cracking still having a tire box, a heating chamber communicating with the lire box, a flue communicating with i the heating Qhamber, a battery of oil heatmunicating with the heating chamben at one end, a flue communicating with the heatling chamber at the other end, and means for diluting the products ot' combustion fromthe lire box with hot gases at a lower temperature than the gases from the tire box whereby the products of combustion are tempered and diluted before they are passed through the heating chamber.

9. An oil crackingastill having a heating chamber, oil heating surfaces adapted to be externally heated therein, a fire box comlmunieating with the'said chamber at one end, a flue communicating with the chamber at the other end, and means for tempering the hot products of combustion from the tire vbox by the introduction thereinto of hot gasesfrom the heating chamber whereby the heatingl gases from the lire box are tempered by the returned heated gases and the resulting mixture is passed through the heating chamber. t p

10. An oil cracking still having a'heating chamber with oil heating surfaces adapted to be externally heatedA therein, a ire box communicating with said chamber, and means for diluting the hot products of combustion from the ire box, at a point between the lire box and the. heating chamber, with gas at a temperature approximately equal to that of the exit gases from said heating chamber. 4

11. A tubular oil still having a heating chamber with oil heating tubes adapted to be externally heated therein, a fire box communicating with said chamber, means for preventing direct radiation from the lire box against lthe tubes, and means for diluting the hot products of combustion from said fire box with heated gas at a lower temperature, at apoint between the lire box and the heating chamber.

12. An oil/'cracking still having a heating chamber with oil heating surfaces adapted to be externally heated therein, a lire heating chamber at a point between the fir@ box and the heating chamber.

hot waste heating gases from near the outlet of the heating chamber and admixing them with the products of combustion from the fire box at a point between the fire box and the heating chamber, and means for circulating the admixed gases through the heating chamber generally counter current to the circulation of oil through the heatin'g tubes.

14. tubular oil cracking still having a heating chamber with oil heating tubes adapted to be externally heated therein, and with bailesfor causing the heating gases toy pass therethrough in a series of passes and in a generally downward direction, a furnace chamber communicating with the heating chamber near the upper end and a stack near the lower end, and means for returning a part of the cooler gases from near the outlet of the heating chamber and admixing them with the products of combustion from the furnace chamber prior to entry into the heatingchamber.

JOHN E. BELL. 

